Magnetocaloric effect in {[Fe(pyrazole)$_4$]$_2$[Nb(CN)$_8$]$\cdot$4H$_2$O}$_n$ molecular magnet

Abstract

Magnetocaloric effect in {[Fe(pyrazole) 4 ] 2 [Nb(CN) 8 ]•4H 2 O} n molecular magnet is reported. It crystallizes in tetragonal I4 1 /a space group. The compound exhibits a phase transition to a long range magnetically ordered state at T c ≈8.3 K. The magnetic entropy change ∆S M as well as the adiabatic temperature change ∆T ad due to applied field change µ 0 ∆H=0.1, 0.2, 0.5, 1, 2, 5, 9 T as a function of temperature have been determined by the relaxation calorimetry measurements. The maximum value of ∆S M for µ 0 ∆H = 5 T is 4.9 J mol −1 K −1 (4.8 J kg −1 K −1 ) at 10.3 K. The corresponding maximum value of ∆T ad is 2.0 K at 8.9 K. The temperature dependence of the exponent n characterizing the field dependence of ∆S M has been estimated. It attains the value of 0.64 at the transition temperature, which is consistent with the 3D Heisenberg universality class.